This invention relates to a fuel supply control method for multicylinder internal combustion engines, which effects sequential fuel injections into cylinders of the engine in synchronism with pulses of a signal indicative of predetermined crank angles of the engine from engine rotational angle sensing means, and more particularly to a fuel supply control method of this kind, which is adapted to continue the engine operation by preventing engine stalling in the event of abnormality in the engine rotational angle sensing means.
A fuel supply control method for multicylinder internal combustion engines has generally been employed, which determines the fuel injection timing into each of cylinders of the engine with reference to pulses of a cylinder-discriminating signal (hereinafter called "the CYL signal pulses") generated by a cylinder-discriminating sensor (hereinafter called "the CYL sensor") at a predetermined crank angle of a particular one of the engine cylinders as well as pulses of a crank angle position signal (hereinafter called "the TDC signal pulses") generated by an engine rotation sensor (hereinafter called "the Ne sensor") at predetermined crank angles of the engine corresponding to respective cylinders of the engine, and injects required amounts of fuel through fuel injection valves in accordance with the fuel injection timing thus determined.
According to this fuel supply control method, in order to ensure smooth operation of the engine, it is an essential requisite that the CYL signal pulses and the TDC signal pulses, which determine the timing of fuel injection into each cylinder of the engine, should be accurately generated in proper sequence. In multi-cylinder engines in general, when the cylinder-discriminating signal detecting system (hereinafter called "the CYL detecting system") and the engine rotational angle detecting system (hereinafter called "the Ne detecting system") are in normally operative states, an injection of fuel is effected into a cylinder #1 upon generation of a pulse of the TDC signal immediately following a pulse of the CYL signal, followed by sequential fuel injections into cylinders #3, #4, and #2 in the mentioned order, upon generation of respective subsequent pulses of the TDC signal sequentially generated. Thereafter, a fuel injection is again effected into the cylinder #1 upon generation of a pulse of the TDC signal immediately following a pulse of the CYL signal which immediately follows the pulse of the TDC signal corresponding to the last cylinder #2. In this sequence, sequential fuel injections into the cylinders #1-#4 are repeated.
However, in the event of the occurrence of an abnormality in the Ne detecting system such that TDC signal pulses are not generated at the aforementioned predetermined crank angles of the engine, sequential fuel injections into the engine cylinders cannot be effected in a proper manner, even causing engine stalling.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a fuel supply control method for internal combustion engines, which enables the engine to continue operating even while engine rotational angle position sensing means is out of order, by effecting simultaneous fuel injection into all of the cylinders.
According to the invention, there is provided a method of injecting fuel into cylinders of a multicylinder internal combution engine, having cylinder-discriminating means for generating a pulse of a cylinder-discriminating signal each time a predetermined crank angle position of a particular one of the cylinders is assumed, and engine rotational angle sensing means for generating a pulse of a crank angle position signal each time a predetermined crank angle position of each of the cylinders is assumed, in predetermined sequence starting with a predetermined cylinder corresponding to a first pulse of the crank angle position signal generated after each pulse of the cylinder-discriminating signal and in synchronism with pulses of the crank angle position signal.
The method of the invention is characterized by the following steps: determining whether or not a pulse of the crank angle position signal has been generated between an immediately preceding pulse and a present pulse of the cylinder-discriminating signal; and when no pulse of the crank angle position signal has been generated between an immediately preceding pulse and a present pulse of the cylinder-discriminating signal, effecting simultaneous fuel injections into all the cylinders of the engine upon generation of the present pulse of the cylinder-discriminating signal.
Preferably, the engine rotational angle sensing means is determined to be abnormal when the simultaneous fuel injections have been effected consecutively a predetermined number of times.
The above and other objects, features and advantages of the invention will be more apparent from the ensuing detailed description taken in connection with the accompanying drawings.